(1) Field of Invention
The invention relates to a sensor system for remotely detecting a gas-liquid interface on a solid body.
(2) Description of the Prior Art
Determining the location of a liquid contact location is a common problem when dealing with gas-liquid interfaces. This problem occurs in determining the level of liquid in a tank, location of a waterline on a vessel or buoy, or positioning of a cavity about a high-speed underwater vehicle.
There is a trade-off between sensor spatial resolution and complexity. A sensor array sized to cover a large area must reduce the overall number of sensors or use a prohibitively complex processing system. For example, pressure sensors are a common method of detecting the presence of either gas or liquid at a single point. Making these measurements over a large area requires an array of sensors which can be tedious to work with and consume large amounts of processing time.
Sensors based on electrical conductance/resistance changes are also known in the art, but are also generally limited to small surface areas, which makes them impractical for large-scale applications such as vessels or structures.
Another type of sensor, an optical sensor, utilizes the principles of total internal reflectance to distinguish a gas-liquid interface. Several prior art patents describe sensors that make use of the principle of total internal reflection for detecting the presence of moisture or dirt on a vehicle windshield (e.g., U.S. Pat. No. 6,052,196 to Pientka et al., U.S. Pat. No. 6,232,603 to Nelson, U.S. Pat. No. 6,084,519 to Coulling et al.). While these sensors typically are incorporated into a feedback control system, they only measure locally and do not provide specific information about the location of contact of gas-liquid interfaces with the surface. Moreover, the sensors are not configured to provide information for a larger area.
It is desireable to have sensors which can accurately determine the location of a gas-liquid interface over a large surface. As previously mentioned, dynamically and remotely detecting the location of a gas supercavity on a supercavitating vehicle is vital for vehicle control and model validation, yet a reliable method of remotely detecting the closure location is lacking. Another application is detecting the location of contact of a free-surface on a ship hull or buoy, critical for vessel control and safety. Finally, application of such a sensor to a floating platform or other marine structure would provide important information on the structure's submergence, preventing it from being raised or lowered beyond safety margins or structural limits.
It is desirable to have a sensor which can monitor a gas-liquid interface and continuously provide feedback over a large area without increasing the need for the number of sensors.
It is further desirable to have a device which has the sensitivity to collect data variations from single point to a large surface area.
It is further desirable to have a device which may utilize such data in a feedback loop to control a cavitator or other object.